<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    .tudou{
      position: relative;
      width: 444px;
      height: 320px;
      margin: 100px auto;
      background: pink;
    }
    .tudou img{
      width: 100%;
      height: 100%;
    }
    .mask{
      display: none;
      width: 100%;
      height: 100%;
      position: absolute;
      left: 0;
      top: 0;
      background: rgba(0,0,0,0.4) url("../img/arr.png") no-repeat center;
    }
    .tudou:hover .mask{
      display: block;
    }
  </style>
</head>
<body>
<div class="tudou">
<img src="../img/tudou.jpg">
  <div class="mask"></div>
</div>
</body>
</html>
